Odd display issues in minimized browser

Member

I just wanted to know if you could have a look at this code for a site. For some reason when you minimize and change the size of the browser elements of the site change.

For example when you scroll across parts of the site are not displayed. However when you click the browser back to full screen the site displays normally again.

Could someone tell me what makes the aspects of the site display like this. For example the footer is black when I make the browser have the size its ok but as soon as you scroll horizontally with the modfied browser half the page stops being displayed correctly. I will attach a screen shot and full code of the site.